Sombutboon, J., Prakas, N., & Eiu-Seeyok, B. (2019). Happiness of Thai Elderly in Thailand 4.0. Journal of Phrapokklao Nursing College, Chanthaburi, 30(2), 219–228. Retrieved from https://he01.tci-thaijo.org/index.php/pnc/article/view/199567